Women's Health

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Low Birthweight PORT links high maternal ferritin levels
during the second trimester with preterm birth

Women who have too high a level of ferritin in their blood
(usually a measure of serum iron) during the second trimester of
pregnancy are three times more likely to deliver preterm infants
than other women, according to a study by the Low Birthweight
Patient Outcomes Research Team (PORT), which is supported by the
Agency for Health Care Policy and Research (PORT contract
282-92-0055).

Growing evidence indicates that preterm birth is associated with
upper genital tract infections. The PORT investigators suggest
that elevated serum ferritin, which has been linked to acute and
chronic infections, may be an acute-phase reactant (a substance
that increases or decreases in conjunction with inflammatory
processes) associated with an upper genital tract infection in
these women. Ordinarily, serum ferritin decreases after the 16th
week of gestation.

The PORT researchers, led by Robert L. Goldenberg, M.D., of the
University of Alabama at Birmingham, evaluated the relationship
between spontaneous preterm delivery and infections such as
acute-phase reactants, levels of maternal iron, and protein
status. They obtained serum samples at 24 weeks gestation from 94
economically disadvantaged pregnant women.

Women with serum ferritin levels at least 42.0 mg/L had three
times greater odds of delivering earlier than 32 weeks compared
with women whose serum ferritin levels were lower than this
value. This three-fold greater risk of preterm birth remained
even after other contributing factors, such as maternal age,
race, and history of a previous low birthweight infant, were
taken into account. The other indexes of iron status and
acute-phase reactants (for example, C-reactive protein) were not
significantly associated with gestational age at birth. The
effect of iron deficiency anemia on pregnancy outcomes was
conflicting. Neither serum copper nor zinc concentrations were
associated with gestational age at birth, according to the
researchers.

In a related editorial, Dr. Goldenberg points out that babies
born to women who are obese before becoming pregnant may not
benefit from maternal dietary supplementation with trace metals
or vitamins as do babies born to thinner women. He notes that
previous studies by the Low Birthweight PORT have shown that the
increase in fetal growth due to maternal zinc supplementation
occurs predominantly in lean mothers.

Also, two recent studies carried out by others (Shaw, Velie, and
Schaffer, JAMA 275(14):1093-1096, 1996; Werler, Louik, Shapiro,
et al., JAMA 275(14):1089-1092, 1996) show that folic acid
supplementation around the time of conception reduces incomplete
closure of the fetal neural tube (neural tube defects, NTDs) at
around 4 weeks' gestation in lean but not obese women, and that
obesity itself is a risk factor for NTDs. However, folic acid,
even in large quantities, may not be able to overcome other as
yet unknown factors that may be associated with an increase in
NTDs in the infants of obese women.

For more details on the study or editorial, see "Serum ferritin:
A predictor of early spontaneous preterm delivery," by Tsunenobu
Tamura, M.D., Dr. Goldenberg, Kelley E. Johnston, B.S., and
others, which appears in the March 1996 Obstetrics &
Gynecology 87(3), pp. 360-365; and "Prepregnancy weight and pregnancy
outcome," by Dr. Goldenberg, in the April 10, 1996, issue of the
Journal of the American Medical Association 275(14), pp.
1127-1128.

Pregnant black women have more than twice the rate of chronic
hypertension than women of other races. This may contribute to
the greater incidence of low birthweight, preterm deliveries, and
infant sickness and death among black women in the United States,
according to a recent study by a team of researchers from the
Agency for Health Care Policy and Research-supported (HS07400)
MEDTEP Minority Research Center at Morehouse School of Medicine
in Atlanta, GA. They found that hypertensive black women are at
three-fold greater risk of hemorrhaging before delivery
(antepartum hemorrhage) than black women whose blood pressure is
within normal limits, an association not seen among other U.S.
women. This hemorrhaging can be caused by premature separation of
the placenta, placenta previa (a condition in which the placenta
blocks the cervix), blood clotting problems, or other
problems.

The researchers analyzed medical records data from the National
Hospital Discharge Survey for the period 1988-1992 and found that
the incidence of pregnancy-induced hypertension was 38.2 per
1,000 deliveries among all U.S. women who delivered babies in a
hospital during the study period, and that black women accounted
for 18 percent of all 628,933 deliveries in which the mothers
were hypertensive. The incidence of hypertension among black
women was 64.2 per 1,000 deliveries compared with 48.6 per 1,000
deliveries for other women. The rate of chronic hypertension
preceding pregnancy was about 2.5 times higher among black women
(25 per 1,000 deliveries) compared with other women (10.5 per
1,000 deliveries). Chronic hypertension is more likely than
pregnancy-induced hypertension to lead to pregnancy
complications. For example, development of late pregnancy
toxemia, which can lead to convulsions and coma (preeclampsia and
eclampsia), was about four times higher among women with chronic
hypertension preceding pregnancy.

See "Maternal hypertension and associated pregnancy complications
among African-American and other women in the United States," by
Aziz R. Samadi, M.D., M.P.H., Robert M. Mayberry, M.P.H., Ph.D.,
Akbar A Zaidi, Ph.D., and others, in the April 1996 issue of
Obstetrics & Gynecology 87(4), pp. 557-563.